The present invention relates to a polycarbonate resin composition and more particularly to a polycarbonate resin composition which is freed of phenolic residues and thus it is capable of providing a molding having an excellent appearance.
In recent years, a reduction in the weight of material has been extensively made for cars, home electric appliances and so forth from a viewpoint of energy saving. With this trend, replacement of glass with plastics has been accelerated. As such replacements, polycarbonate resin moldings are considered hopeful because of their excellent transparency, mechanical characteristics and dimensional stability.
A polycarbonate resin is molded by techniques such as injection molding, blow molding, compression molding and rotational molding. If, however, unreacted starting materials (e.g., bisphenol A) and phenolic residues as derived from carbonate oligomers remain unremoved in the polycarbonate resin, they attaches to a mold, deteriorating the appearance of moldings. Removal of such attaches needs cleaning of the mold and during this cleaning process, the molding should be stopped, which is undesirable from an economic standpoint.
Another means to overcome the above problem is to remove the phenolic residues from the polycarbonate resin. For this purpose, it suffices that the polycarbonate resin is washed more thoroughly. In this case, however, a much longer time is needed for the removal operation and productivity is seriously reduced, which is disadvantageous from an industrial standpoint. Under such circumstances, various attempts to remove the residues by compounding suitable additives to the resin have been made. For example, Japanese patent publication No. 44552/1976, Japanese patent application Laid-Open Nos. 84352/1980 and 81245/1985 disclose that aliphatic carboxylic acid esters, aliphatic alcohols and the like are compounded to the polycarbonate resin to remove halogen or to improve releasability at the time of molding or to increase heat resistance. If, however, the above known compounds are used alone, the effect of removing phenolic residues is small.